The present invention relates to an improved method of false twist spinning entailing the method steps:
that a fiber sliver is drafted to a desired yarn count in a drafting mechanism and is delivered as drafted fiber sliver from a delivery roller pair of the drafting mechanism, PA0 that the drafted fiber sliver thereafter is sucked in substantially spiral fashion into a converging passage and is thereafter taken-up by a false twist member, and PA0 that by means of the false twist member a part of the drafted fiber sliver is twisted to a so-called false-twisted yarn core with the formation of a spinning triangle.
The present invention further relates to an improved apparatus for false twist spinning comprising a drafting mechanism for delivering a drafted fiber sliver to a suction passage and with a false twist member arranged after the suction passage, the suction passage converging to its narrowest location or throat in a direction towards the false twist member.
The problems associated with yarns produced by the false twist spinning method during further processing to finished fabrics lie substantially in the uniformity or evenness, strength and extensibility. For example, non-measurable, repeating weak places, even when the measured strength of the yarn is much higher, represent substantial disadvantages in warping and weaving processes, and nops reduce the value of the finished fabric even where the yarns produce no problems in the subsequent processing stages.
A method and an apparatus of the general character heretofore described are known from Swiss Pat. No. 615,467.
In this known process, and in this known apparatus, which is illustrated schematically and partly in section in accompanying FIG. 1, a fiber sliver 2 delivered to a drafting. mechanism 1 is standardized or calibrated by funnels 5 and 6 respectively provided before an infeed roller pair 3 and an intermediate roller pair 4, and is guided by an apron pair 8 extending from the intermediate roller pair 4 towards the delivery roller pair 7 (the roller pairs are indicated with broken lines).
In the converging space of the delivery roller pair 7 a further funnel 9 is provided for collecting the edge fibers F and to avoid as far as possible loss of these edge fibers.
In the method according to the prior art, the fiber sliver 2 is delivered from the apron pair 8 (of which only the lower apron is shown) with a width BA and is fed to the nip line K formed by the delivery roller pair 7.
In the converging space of the delivery roller pair 7, the fiber sliver undergoes spreading due to the peripheral air of the rotating delivery roller pair 7 transported into this space and escaping in the axial direction; this spreading is limited by the funnel 9 to a width BB.
Due to the difference between the width BB and the smaller width BC of the spinning triangle, the aforementioned edge fibers F occur which are drawn by suction into a suction passage 10 and at the latest at the narrowest location or throat of the suction passage, that is before the throttle position 11. For the most part these edge fibers are caught up by the rotating false-twisted yarn core 12. The twist in the yarn core 12 arises from the pneumatic false twist member 13 arranged downstream from the throttle position 11.
The essential disadvantage of this method lies in inadequate uniformity or evenness of the yarn in respect of weight-evenness, weak places and nops. Also, the strength of the yarn is substantially lower than that of the normal ring-spun yarns. This inadequate regularity is substantially due to the fact that the described fiber spreading occurs randomly and uncontrolled.